Low-concentration nitroglycerin gel applied topically produces localized vasodilation — the same mechanism as nitrate heart medications but concentrated locally. Some urologists actually prescribe low-dose nitroglycerin topical for Raynaud's of the penis and ED. The temporary engorgement effect is real and fast. The concerns: headache from systemic absorption (real, reported), potential for hypotension if combined with PDE5 inhibitors, skin sensitization with repeated use. This is in the same category as pumping — real temporary effect, zero permanent structural change, requires management before every use. Some guys find it useful. Know what it is.
— NitroGelNick